Not for 3.5, as it extends, rather than replaces 2.0.
However, for 4.0 I think it could work for server apps, but I am not sure if it would work everywhere with all type of applications for all different versions.
I wonder, though, why you'd want to..... IMO, I wouldn't take the risk.
BTW: for questions not directly related to the book, you're better off asking them in a more general .NET category here:
http://p2p.wrox.com/asp-net-4-539/
Cheers,
Imar